title: Increased risk of breast cancer associated with long-term shift work in Canada.
abstract: OBJECTIVE
  Long-term night work has been suggested as a risk factor for breast cancer; however, additional studies with more comprehensive methods of exposure assessment to capture the diversity of shift patterns are needed. As well, few previous studies have considered the role of hormone receptor subtype.
  
  
  METHODS
  Relationships between night shift work and breast cancer were examined among 1134 breast cancer cases and 1179 controls, frequency-matched by age in Vancouver, British Columbia, and Kingston, Ontario. Self-reported lifetime occupational histories were assessed for night shift work, and hormone receptor status obtained from tumour pathology records.
  
  
  RESULTS
  With approximately one-third of cases and controls ever employed in night shift work, associations with duration demonstrated no relationship between either 0-14 or 15-29 years, while an association was apparent for ≥30 years (OR=2.21, 95% CI 1.14 to 4.31). This association with long-term night shift work is robust to alternative definitions of prolonged shift work, with similar results for both health and non-health care workers.
  
  
  CONCLUSIONS
  Long-term night shift work in a diverse mix of occupations is associated with increased breast cancer risk and not limited to nurses, as in most previous studies.
authors.affiliation: Department of Public Health Sciences and Queen's Cancer Research Institute, Queen's University, Kingston, Ontario, Canada.
authors.forename: Anne
authors.initials: A
authors.lastname: Grundy
authors.forename: Harriet
authors.initials: H
authors.lastname: Richardson
authors.forename: Igor
authors.initials: I
authors.lastname: Burstyn
authors.forename: Caroline
authors.initials: C
authors.lastname: Lohrisch
authors.forename: Sandip K
authors.initials: SK
authors.lastname: SenGupta
authors.forename: Agnes S
authors.initials: AS
authors.lastname: Lai
authors.forename: Derrick
authors.initials: D
authors.lastname: Lee
authors.forename: John J
authors.initials: JJ
authors.lastname: Spinelli
authors.forename: Kristan J
authors.initials: KJ
authors.lastname: Aronson
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000378:metabolism; D001943:Breast Neoplasms / Q000453:epidemiology / Q000209:etiology* / Q000378:metabolism; D001955:British Columbia / Q000453:epidemiology; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008593:Menopause; D008875:Middle Aged; D009784:Occupational Diseases / Q000453:epidemiology*; D009864:Ontario / Q000453:epidemiology; D011960:Receptors, Estrogen / Q000378:metabolism; D011980:Receptors, Progesterone / Q000378:metabolism; D012307:Risk Factors; D014940:Work Schedule Tolerance / Q000502:physiology*; D055815:Young Adult
chemical_list: D014408:Biomarkers, Tumor; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone